+146. Shell and beads.+ Shells had very great convenience for money and their value was increased by the fact that ghosts dwelt in them. Cowries were early used as money, 2200 of them equaling in value one franc.[298] They are now losing currency. On Fernando Po bits of achatectonia shells are made into belts and used as currency.[299] A far less widespread shell of a sea snail was used in northern Transvaal.[300] Other cases of the use of shells will be given below. A dress pattern of cotton cloth, seven ells, called a "tobe," is a unit of monetary reference through the Sudan.[301] Another money in the same region is the iron spade, with which tribute is paid to the petty rulers of eastern Equatoria. The spades are made of native iron and are used upon occasion to cut down the grass.[302] Expeditions into the Niam Niam territories always have a smith with them whose duty it is to make rings of copper and iron wire, with a square section, for minor purchases.[303] The currency of beads has greatly lessened wherever more useful objects of European manufacture have become known.[304] Forms of the lance head are used to buy a wife, who costs twenty or thirty of them.[305] Further south von Goetzen found brass wire, in pieces fifteen to thirty-five centimeters long, in use as money, not being an article of use, but a real money used to store value, to buy what is wanted, and to pay taxes for protection against one's forest neighbors.[306] Formerly, when beads were still used as money, each district had its own preferred size, shape, and color. Travelers found that the fashion in a district had changed since the information was obtained, relying on which they had provided themselves. This is, however, evidently a part of the operation of differentiating the predominant ware.[307]